External genitalia in cockroach consist of small irregular chitinous plates known as

Options

A. Seminal vesicles
B. Collaterial gland
C. Phallomeres
D. Abdominal scierites

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question:**
The question asks about the small irregular chitinous plates that form the external genitalia in cockroaches.

2. **Identifying the Options:**
The options provided are:
- Seminal vesicle
- Collateral gland
- Phalomaeus
- Abdominal sclerites

3. **Analyzing Each Option:**
- **Seminal Vesicle:** This is part of the male reproductive system but is not made of chitin and does not form the external genitalia.
- **Collateral Gland:** This gland is associated with the female reproductive system and produces secretions for egg protection, not related to the external genitalia of males.
- **Phalomaeus:** This is a chitinous structure found in male cockroaches that surrounds the male gonophore, forming part of the external genitalia.
- **Abdominal Sclerites:** These are hard parts of the insect's body and do not pertain to the genitalia.

4. **Conclusion:**
Based on the analysis, the correct answer is **Phalomaeus**, as it consists of small irregular chitinous plates that form the external genitalia in male cockroaches.

**Final Answer:**
The external genitalia in cockroach consist of small irregular chitinous plates known as **Phalomaeus**.

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